Though there are many different versions of RNN, the following is the widely used one [1]}.
\(&\mathbf {h}_t = \rho (\mathbf {W}_h \mathbf {x}_t + \mathbf {U}_h \mathbf {h}_{t-1} + \mathbf {b}_h) \\&\mathbf {y}_t = \rho (\mathbf {W}_y \mathbf {h}_t + \mathbf {b}_y)\) 
